多对多关联映射(单向)

inverse属性：

inverse主要用在一对多和多对多双向关联上，inverse可以被设置到集合标签<set>上，默认inverse为false，所以我们可以从"一"一端和"多"一端维护关联关系，如果设置成inverse为true，则我们只能从多一端来维护关联关系。

inverse属性，只影响数据的存储，也就是持久化。

一个用户可能拥有多个角色（user-->role）

package com.jonsion.hibernate;

public class Role {

private int id;

private String name;

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}

package com.jonsion.hibernate;

import java.util.Set;

public class User {

private int id;

private String name;

private Set roles;

public Set getRoles() {

return roles;

}

public void setRoles(Set roles) {

this.roles = roles;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

      "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

          "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping >

<class name="com.jonsion.hibernate.Role">

<id name="id">

<generator class="native"/>

</id>

<property name="name"/>

</class>

</hibernate-mapping>

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

      "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

          "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping >

<class name="com.jonsion.hibernate.User">

<id name="id">

<generator class="native"/>

</id>

<property name="name"/>

<set name="roles" table="t_user_role">

<key column="userid"/>

<many-to-many class="com.jonsion.hibernate.Role" column="roleid"/>

</set>

</class>

</hibernate-mapping>

package com.jonsion.hibernate;

import java.util.HashSet;

import java.util.Iterator;

import java.util.Set;

import junit.framework.TestCase;

import org.hibernate.Session;

import org.hibernate.Transaction;

public class Many2ManyTest extends TestCase{

public void testSave1(){

Session session=null;

Transaction tx=null;

try{

session=HibernateUtils.getSession();

tx=session.beginTransaction();

Role r1=new Role();

r1.setName("大堂经理");

session.save(r1);

Role r2=new Role();

r2.setName("出纳");

session.save(r2);

Role r3=new Role();

r3.setName("业务员");

session.save(r3);

User user1=new User();

user1.setName("阿希");

Set r1role=new HashSet();

r1role.add(r1);

r1role.add(r2);

user1.setRoles(r1role);

User user2=new User();

user2.setName("阿雅");

Set r2role=new HashSet();

r2role.add(r2);

r2role.add(r3);

user2.setRoles(r2role);

User user3=new User();

user3.setName("阿杜");

Set r3role=new HashSet();

r3role.add(r1);

r3role.add(r2);

r3role.add(r3);

user3.setRoles(r3role);

session.save(user1);

session.save(user2);

session.save(user3);

tx.commit();

}catch(Exception ex){

ex.printStackTrace();

tx.rollback();

}finally{

HibernateUtils.closeSession(session);

}

}

public void testLoad1(){

Session session=null;

Transaction tx=null;

try{

session=HibernateUtils.getSession();

tx=session.beginTransaction();

User user=(User)session.load(User.class, 3);

System.out.println(user.getName());

for(Iterator it=user.getRoles().iterator();it.hasNext();){

Role role=(Role)it.next();

System.out.println(role.getName());

}

tx.commit();

}catch(Exception ex){

ex.printStackTrace();

tx.rollback();

}finally{

HibernateUtils.closeSession(session);

}

}

}